So, what is left to say on the topic of electronic plumbing? Plenty, especially if you are in the business of designing systems that rely on this evolving technology.
Asking the Right QuestionsElectronics in the washroom is not a single answer to a single question. Just as the no-touch washroom holds numerous benefits, there are also various means of achieving this end. It is important when engineering an electronic washroom solution to ask the right questions before you get started.
What are the components?No-touch faucets and washfountains incorporate four basic components: a solenoid valve assembly, a temperature mixing valve, a sensor activated electronic control and a transformer or power supply.
A standard solenoid valve, similar to the type contained in washing machines and dishwashers is a logical choice when engineering a reliable, electronically-controlled plumbing fixture. Such a valve contains a minimum number of moving parts, is virtually maintenance-free and operates in widely-varied water conditions and temperatures. It is opened and closed electrically and supplies water only when it is needed. Therefore, it has all the characteristics of the perfect metering valve.
While electronic temperature mixing valves are available, they are normally less reliable and more expensive than mechanical temperature mixing valves. Mechanical temperature mixing valves, such as those used in washfountains, are usually preset to provide water at approximately 105 F, which is warm, but well below the scald temperature. Mechanical mixing valves should shut the water flow off if cold or hot water pressure is lost. Some electronic faucets have a mechanical mixing valve built in and a control lever on the side which enables the user to adjust the water temperature.
Selecting the right electronic control system for no-touch fixtures is more difficult because of the wide variety of electronic sensing technology available. Understanding how each sensor technology operates, and the environmental factors which affect its performance will help you decide which type of device best meets your needs.
What are my sensor options?The challenge for any sensor technology is similar to picking out a single voice within a crowded room of speakers. That is to say, it must be able to distinguish relevant signals from irrelevant ones. This is most commonly done using an active infra-red detection/activation system.
A standard application of infra-red technology in plumbing applications is a diffuse reflective proximity system. This system relies upon an infra-red light emitting diode (LED) which illuminates the hand wash area and a photo detector which activates a faucet, for example, in response to changes in the reflected light intensity within its field. This type of sensor is small enough to fit easily into a faucet and is relatively inexpensive.
Other infra-red sensor technologies include optical position sensing devices (PSDs) and dual beam sensors. A dual beam sensor is essentially two position sensing devices. These rely on a collimated infra-red beam of light reaching out from the sensor into the hand basin. A photodector is focussed on a point of that infra-red beam where activation of the solenoid valve is required. When a hand is moved to that intersection point, the photodector will receive the reflected light off the hand and activate the solenoid valve.
Less common in plumbing applications are heat activated passive infra-red sensors and ultrasonic sensors. Passive infra-red sensors work using technology similar to that which activates approach lights on homes. The major disadvantage of these sensors is that they will not activate if the trigger and the environment are the same temperature. Thus, in a faucet application, if the users hands are the same temperature as the hand basin, the sensor will not work.
What about Power Sources?Electronic faucets can be powered by either low-voltage wiring or batteries. The advantage of battery operated sensors and valves is that they require no power outlet, and so do not require installation by an electrician. Battery operated infra-red faucets will operate for well over a year or provide over 150,000 activations before the AA batteries require replacement.
Another electronic solution is the battery operated and 24VAC pushbutton mechanism used in timed showers and washfountains. Although these require "touch", they are extremely reliable and avoid most of the environmental challenges optical sensors face. Their timing periods are also extremely accurate.
Whichever power source is used, it is good practice to equip electronic plumbing units with power surge suppressors. This is especially true in environments likely to experience wide power surges, such as rest stops at the end of a power line grid, or units reliant upon well pumps, which can produce a power surge when they switch off.
What role does environment play?Given that an electronic sensor's task is to monitor its environment, it is important for engineers designing electronic plumbing equipment to consider potential pitfalls to the technology's optimum performance. Some of these challenges are very difficult to predict, but by studying past difficulties we avoid future frustration.
Lighting. If the room which the sensor is used in has a clear window, at certain times of the year, the sensor may look directly at reflected light. Such specular reflections, similar to the reflection of the sun on water, are well beyond any optical sensor's limits. As a result, the sensor may operate when no one is present. When designing a restroom, it is therefore recommended that any optical sensors used not face a window. Frosted glass or window treatments can also be employed to eliminate this problem.
Similarly, newer high efficiency florescent lamps in close proximity (1 to 3 feet) of the optical sensor can overpower the signal the sensor is detecting and activate the faucet unpredictably. These florescent lights operate at a frequency between 30 and 50 Khz. This frequency often drifts as the lamp warms up, and the output of these lamps contains a fairly large amount of near infra-red which can interfere with the sensor signals and activate the faucet erratically. For this reason, ceiling lighting is recommended for use with optical sensors.
Signal Confusion. Sensors can sometimes be confused by the signal from another sensor within the same room. For this reason, it is important to make sure that the field of view of one sensor does not include another sensor. Mirrors on the wall opposite the sensor can also reflect the signal and activate the sensor, as can reflections from a sunlit window. In addition, highly polished surfaces such as stainless steel bowls can confuse an optical sensor, particularly when water is beading on the surface of the bowl. In these situations, dual beam sensors and position sensing devices will operate more reliably than diffuse reflective sensors.
Demanding Environments. The very nature of public restrooms presents a number of additional challenges which the plumbing engineer would do well to consider when designing no-touch systems.
Fixtures in washrooms and locker rooms are exposed to a great deal of moisture in their everyday use and cleaning. It is important, therefore, for no-touch sensors to have their electronics "potted" or conformal coated for protection from high or condensing humidity.
High traffic washroom environments also subject plumbing fixtures to heavy use and expose them to potential vandalism. As a general rule, a smaller sensor offers a smaller target for mishaps, intentional or otherwise. It is also wise to locate the sensing device within the fixture itself, rather than in a remote location such as the wall above the fixture where it is in open view. A robust diffuse reflective sensor that is concealed from plain sight and protected within the fixture body itself most effectively deters vandalism and this approach is recommended in public washrooms. The optics of the diffuse reflective sensor and dual beam sensor are protected by a plastic window which works as an infra-red filter and serves to protect the sensor's emitter and detector from vandalism.
While generally less prone to performance problems, dual beam sensors and position sensing devices are physically larger and require separated transmitters and receivers. These technologies thus offer increased opportunities for vandals seeking to disable the unit.
What about Control Settings?Most new optical sensors are driven by a small microprocessor with programmable adjustments allowing control of the sensor's range as well as its sensitivity to motion and the time the sensor will keep the water flowing once it is activated.
Proper flow timing in an electronic faucet must allow users to remove their hands from the water flow for two to three seconds for applying or lathering soap. Continued water flow during this time ensures a smoothly controlled hand washing experience.
Another important flow time consideration, particularly in vandal-prone washroom settings, is an automatic shut off feature. The fixture's valve should automatically close if a non-moving presence is detected for a preset time period. This prevents vandals from attempting to trigger continuous water flow by placing an object over or in front of the sensor unit.
What are Some Applications?Water faucets and washfountains are obvious candidates for electronic plumbing technology. As discussed above, electronic plumbing solutions hold clear benefits for public washrooms where vandalism is an issue.
In addition, no-touch technology is ideal in applications where hygiene is of critical importance. This includes food preparation areas, as well as hospitals and restaurants. In each of these locations, contaminated tapware poses potential public health risks. Laboratories where scientific experiments require sterile environments are another area well-suited for no-touch plumbing fixtures.
Other areas where electronics have entered the washroom/locker room arena to the include automatic shower timers, flush systems, hand dryers and soap dispensers. These applications rely upon the same type of infra-red activation technology, and face the same challenges discussed relative to electronic faucets.
What are the Benefits?The increased convenience offered by electronic plumbing solutions and their resistance to vandalism spell dramatic benefits to users, facility managers, business owners and the general public.
One hundred and fifty years ago, a Hungarian physician Ignaz Semmelweis first related the failure of doctors to wash their hands with the spread of fatal infections from one patient to another. Today, the Federal Centers for Disease Control and Prevention points out that hand washing is the cheapest and simplest way to break the transmission of disease, but it is also the most underused.
Contributing to this neglect is the perception among public washroom users that contact with the facilities themselves spreads harmful bacteria. Electronic plumbing solutions address both the reality and the perception of unclean washrooms, increasing use and fighting the spread of disease.
Decreased vandalism and increased sanitation translate into fewer maintenance dollars spent by facility managers, who also enjoy the benefits that no-touch washroom fixtures and accessories offer in terms of traffic management. Users in no-touch environments spend less time moving through the washroom and use less water than those who use standard equipment. The result is a reduced utility bill and an easing of congestion, which is especially important in high-traffic environments such as sports stadiums and airports. These results are increased even further in washrooms which employ electronic plumbing solutions in multiple-station fixtures that serve many users simultaneously from a single set of plumbing connections.
Washroom cleanliness also directly impacts a business' bottom line. A study by a consulting firm in Massachusetts shows that in 70% of the cases where a retailer or a restaurant has received a below average customer service score, the restrooms were dirty. The flip side is true as well. In 70% of the cases where the customer service rating was above average, the restrooms were clean. The company also reports that nine out of ten dissatisfied customers never complain, and 30% will never return.
Finally, in barrier-free washroom settings, no-touch fixtures are especially well-suited for meeting requirements as set forth in the Uniform Federal Accessibility Standards (UFAS) and in the ANSI Guidelines for handicapped accessibility.
What Does the Future Hold?Future developments in electronic plumbing are limited only by the imagination, and as we refine the technology driving these systems, we are likely to find electronic plumbing solutions entering the residential market.
These refinements are a response to enthusiasm for electronic solutions within the washroom, both from users and facility managers. As we continue to adapt the capabilities of no-touch technology, managing the demands of users, owners and the general public, we advance the cause of public health while remaining mindful of today's drive to make things easier.